Internal-combustion engine.



W. J. STILL.

INTERNAL COMBUSTION ENGINE. APPLIOATI'ON FILED APR.'14, 1911.

1,015,217. I PatentedJan.16,l912..

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' UNITED STATES PATENT OFFICE.

WILLIAM JOSEPH STILL, OF SOUTHALL, ENGLAND.

INTERNAL-COMBUSTION ENGINE.

Specification of Letters Patent.

Patented J an. 16, 1912.

Application filed April 14, 1911. Serial No. 621,165.

provide for the more effective scavenging of internal combustionengines.

It has been observed by experiment that in engines having a ring ofports at one end of the cylinder acting as exhaust ports and anotherring of ports at the opposite-end acting as scavenging air inlets whichare uncovered by the piston that if the heacLof the latter which co-actswith the ports be suitably concave and presents no irregularities therush of air which enters by the ports occurs in a uniform mass whichdoes not mingle with the products of combustion but acts as a compactmass to expel or push them out of the-ports at the other end of thecylinder. There being no eddies less air is required and more completescavenging is insured if this feature is utilized.

This invention consists therefore in employing a piston with a concavehead free from such projection or the like as can act to break up thegas stream in an engine of the character indicated for this purpose. Thedegree of concavity which is found to yield the best results is a radiusequal to the bore of the cylinder.

The accompanying figure shows diagrammatically one method of carryingthe invention into effect as applied to an engine in which opposedpistons reciprocate in a cylinder.

The cylinder casting a is provided with three rings of ports openinginto the cylinder 9 which comprise b the exhaust ports, 0 thecombustible inlet ports and (Z the scavenging air inlets. The piston cwhich coacts with the latter is provided with a concaved face f theradius of curvature of which is equal to the bore of the cylinder 9. Inthis case as soon as the piston c uncovers the ring of ports 01 air willrush in to effect scavenging but owing to the form of the piston thesame will not break up into eddies or swirl around but will advance as amore or less uniform mass to expel the products of combustion from theexhaust ports Z). The piston h is also shown as having a concaved headbut this feature is not essential and this piston may have any usualform.

It will be understood that in the form described the entry of thecombustible through the ports 0 is delayed in any suitable way untilafter the ports d are just covered again by the piston e.

It will be understood that it is of importance to have the largest portarea possible and that it is also of importance to have a symmetricalport arrangement which features are most easily attained by a portarrangement of the nature above described. It will be understood howeverthat the ports are not necessarily exactly symmetrical or of anyparticular form provided that they do not create such disturbance of theflow of gas that the concave form of the piston is not able to produceany substantial effect.

The admission ports should preferably be made without irregularities ofsurface such as will deflect the inflowing gas from the desireddirection.

Having now described my invention what I claim as new and desire tosecure by Letters Patent is An internal combustion engine having acylinder with inlet ports substantiallyannularly symmetrically disposedaround the same and a piston with concave head adapted to cover anduncover the said ports the radius of curvature of said concave headbeing about equal to the bore of the cylinder; as set forth.

In testimony whereof, I affix my signature in presence of two witnesses.

WILLIAM JOSEPH STILL. VVitnes'ses CYRIL F. L. NURSEY, P. A. OUTHWAITE.

